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/*
* TLS Data Reader
* (C) 2010 Jack Lloyd
*
* Released under the terms of the Botan license
*/
#ifndef BOTAN_TLS_READER_H__
#define BOTAN_TLS_READER_H__
#include <botan/secmem.h>
#include <botan/loadstor.h>
namespace Botan {
/**
* Helper class for decoding TLS protocol messages
*/
class TLS_Data_Reader
{
public:
TLS_Data_Reader(const MemoryRegion<byte>& buf_in) :
buf(buf_in), offset(0) {}
u32bit remaining_bytes() const
{
return buf.size() - offset;
}
bool has_remaining() const
{
return (remaining_bytes() > 0);
}
void discard_next(u32bit bytes)
{
assert_at_least(bytes);
offset += bytes;
}
u16bit get_u16bit()
{
assert_at_least(2);
u16bit result = make_u16bit(buf[offset], buf[offset+1]);
offset += 2;
return result;
}
byte get_byte()
{
assert_at_least(1);
byte result = buf[offset];
offset += 1;
return result;
}
template<typename T, typename Container>
Container get_elem(u32bit num_elems)
{
assert_at_least(num_elems * sizeof(T));
Container result(num_elems);
for(u32bit i = 0; i != num_elems; ++i)
result[i] = load_be<T>(&buf[offset], i);
offset += num_elems * sizeof(T);
return result;
}
template<typename T>
SecureVector<T> get_range(u32bit len_bytes,
u32bit min_elems,
u32bit max_elems)
{
const u32bit num_elems =
get_num_elems(len_bytes, sizeof(T), min_elems, max_elems);
return get_elem<T, SecureVector<T> >(num_elems);
}
template<typename T>
std::vector<T> get_range_vector(u32bit len_bytes,
u32bit min_elems,
u32bit max_elems)
{
const u32bit num_elems =
get_num_elems(len_bytes, sizeof(T), min_elems, max_elems);
return get_elem<T, std::vector<T> >(num_elems);
}
template<typename T>
SecureVector<T> get_fixed(u32bit size)
{
return get_elem<T, SecureVector<T> >(size);
}
private:
u32bit get_length_field(u32bit len_bytes)
{
assert_at_least(len_bytes);
if(len_bytes == 1)
return get_byte();
else if(len_bytes == 2)
return get_u16bit();
throw Decoding_Error("TLS_Data_Reader: Bad length size");
}
u32bit get_num_elems(u32bit len_bytes,
u32bit T_size,
u32bit min_elems,
u32bit max_elems)
{
const u32bit byte_length = get_length_field(len_bytes);
if(byte_length % T_size != 0)
throw Decoding_Error("TLS_Data_Reader: Size isn't multiple of T");
const u32bit num_elems = byte_length / T_size;
if(num_elems < min_elems || num_elems > max_elems)
throw Decoding_Error("TLS_Data_Reader: Range outside paramaters");
return num_elems;
}
void assert_at_least(u32bit n) const
{
if(buf.size() - offset < n)
throw Decoding_Error("TLS_Data_Reader: Corrupt packet");
}
const MemoryRegion<byte>& buf;
u32bit offset;
};
}
#endif
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